The invention relates to the ventilation of a housing, in particular a housing that may contain electronic components, in a land vehicle such as a car, under the engine hood (bonnet).
Ventilation systems formed on a housing or a housing portion that has to house a contents, and has ventilation grids for said contents that are formed from segments of material leaving a gap between them, are already known.
However, it transpires that, in particular when the housing has to contain members that heat up (such as the aforementioned electronic components) or more generally when it is desired to obtain a flow of air (gaseous fluid) in accordance with the expected ventilation of the contents of the housing (for example 0.2 m/s, without recourse to forced air), a conventional ventilation grid proved to be inappropriate.
In addition, to improve the conditions of entry of the gaseous fluid into the housing, but not to the detriment of other possible requirements (see below), according to an important feature of the invention it is recommended that the aforementioned ventilation system be such that said segments of material are arranged at at least two levels offset depthwise in the general direction of entry of the gaseous fluid into the housing or the housing portion through the grid in question, in order to constitute, by grid, a multiple-grid system, the grids being offset depthwise with respect to one another.
Two additional requirements may furthermore be satisfied:
firstly that of providing, at the location of a ventilation grid, an anti-intrusion effect, preventing the intrusion of a solid (such as a thin straight rod) of a set diameter (IP4X standard at the date of filing of the present application);
to provide less expensive molding manufacturing conditions comparable with the requirements of the marketplace.
In this case, according to an additional feature of the invention it is recommended that the ventilation system be such that, between the levels, the segments of material are transversely offset depthwise so that they do not overlap between two adjacent levels.
A complementary (or alternative) way of satisfying the same requirements consists in ensuring that, at two adjacent levels, the segments of material are arranged approximately in a staggered configuration.
Again, to satisfy simple and inexpensive manufacturing conditions, while ensuring that the ventilation system has dimensions suitable for its application, with in addition a favorable effect as regards the amount of air that can be taken into the housing, according to another feature of the invention it is recommended that the segments of material forming the multiple-grid system consist of bars approximately parallel to one another.
In certain cases, the abovementioned ventilation grids may be in contact with small amounts of water (slight local trickling, condensation, etc.).
In this case, in relation to an embodiment of the segments of material in the form of bars, according to another feature of the invention it is recommended that the ventilation system be formed as a projection on the outer face (the opposite face to that directed toward the content of the housing) of the wall (or of at least one of the walls) of the housing that carries the system, and in addition has a slope in one direction.
Thus, the encroachment on the internal space of the housing is avoided and it will be possible to encourage the flow of liquid droplets, along the slope.
Again, to favor the molding manufacturing conditions, while at the same time increasing the strength of the grid system, according to another feature of the invention it is recommended that the system comprise ribbing extending transversely beneath the last level with respect to the direction of flow of the ventilating fluid entering the housing.
As will have already been understood, the ventilation system of the invention is intended to be formed on (and preferably integral with) a housing or a housing portion.
To achieve the aforementioned xe2x80x9cmechanical anti-intrusionxe2x80x9d effect, the system for ventilating this housing, or this housing portion, will preferably be such that the distance between two adjacent segments of material is less than about 1 millimeter (or even 0.8 millimeters).
For the purpose of further improving the flow of air inside the housing, provision is also made according to another feature of the invention for at least two grids, each consisting of one of the multiple-grid systems, to be at least partly located face to face on two opposed walls of the housing, or in a relative situation in the immediate vicinity of such a face-to-face arrangement.
Advantageously, the housing will comprise at least two housing portions cooperating with each other to form a closed complete housing, thus favoring compliance with the aforementioned standard, and making it easier to mount the contents in the housing, or even to replace them in the event of failure.
Again to favor the flow of air (or more generally of the gaseous fluid) for cooling the contents of the housing (most particularly when these are electronic components), according to another feature of the invention it is recommended that the housing be such that:
it comprises first and second offset multiple-grid systems formed in two opposed walls of this housing;
the contents of the housing comprises electronic components based on at least one board installed in the housing, approximately parallel to the levels of the grid systems;
the board(s) fitted with electronic components is(are) drilled with holes for air to flow from one side of the board to the other; and
at least one of these holes and at least one portion of the first and second multiple-grid systems are approximately aligned for an approximately rectilinear flow of air inside the housing, between the first and second grid systems.
As indicated above, if the improved housing of the invention contains electronic components, it is particularly intended to be placed under an engine hood, in a confined space.
One aspect of the invention therefore relates to the use of one or more of the abovementioned ventilation systems on such a housing or housing portion for electronic components, with as feature the fact that unforced air, at atmospheric pressure, is then made to pass through said multiple-grid system(s).
Thus, despite the absence of blown air (or of extracted air), effective cooling of the electronic components will be obtained.
As already indicated, certain features of the ventilation system of the invention are conducive to an inexpensive and effective method of manufacture by molding.
Thus, one of the additional aspects of the invention, allowing a system of offset grids to be manufactured with segments of material not overlapping one another between two adjacent levels, consists of a mold comprising first and second blocks placed approximately face to face and each having a molding face for defining at least one molding cavity for molding said housing portion, the molding face of each block having a crenelation formed from alternating projections and recesses offset from one face to the other so that the projections on one face penetrate the recesses in the other face, in the molding position of the two blocks of the mold.